307 Trepostomatous bryozoan fauna from the Bellevue Limestone, Upper Ordovician, in the Tri-State area of Ohio, Indiana, and Kentucky

Ten genera of trepostomatous Bryozoa, of which one (Parcohallopora: type species Monticulipora ramose d’Orbigny), is new, are described and illustrated. The 16 species included, of which one is new, are: Amplexopora cingulate Ulrich, A. robusta Ulrich; Batostomella gracilis (Nicholson); Bythopora dendrina (James); Dekayia aspera Milne-Edwards and Haime, D. pelliculata Ulrich; Heterotypa frondose (d’Orbigny), H. solitaria Ulrich; Homotrypa curvata Ulrich, H. obliqua Ulrich; Monticulipora mammulata d’Orbigny; Parvohallopora ramosa (d’Orbigny), P. laevigata, n. sp.; Peronopora decipiens Rominger, P. dubia Cumings and Galloway and Amplexopora (?) filiasa (d’Orbigny). An attempt is made to establish the morphological concept of Batostomella gracilis, the type species of Batostomella, and Monticulipora ramosa, because the type material is not available. The generic assignment of Amplexopora (?) filiasa is tentative; forms referred to this species are peculiar in the absence of zooecial bend and presence of many cycles (non-overgrowth) of endozone and exozone withing a zoarium; a new generic name for the species would be in order but is deferred because the original types have not been traced.

A description format is suggested for the qualitative features of the trepostomes. This gives a three-dimensional picture of a zoarium and should be understood better than the separate descriptions of the tangential and longitudinal orientations given by many contemporary workers.

Monticules, including maculae of some authors, are composed of zooecia, megazooecia, mesopores, thicker walls and irregular wall laminae, either singly or in various combinations. Monticules are here suggested to be polymorphic in the trepostomes.

The integrate and amalgamate concept as used morphologically in the trepostomes is confusing and unnecessary. Nature of the wall laminae in longitudinal orientations is described as: (1) convex; (2) angular; (3) convex or angular with concentrations of darker material, either in zooecial boundary zone or prozimal parts of laminae; or (4) abutting at sharp angles along a thing, dark, granular layer. Forms with the last laminar arrangement may be genetically distinct. The dark layer is not, as has been commonly supposed, an optical effect produced by sharply-bending laminae. In many instances, laminae are darker where they are not bent sharply. Microchemical analysis and electron-probe investigations are needed to further evaluate the morphology of the wall.

An analysis of the original definition by Nickles and subsequent authors validates the Bellevue Limestone as a rock-stratigraphic unit. Other alleged biostratigraphic units of the Cincinnatian need to be similarly analyzed before they are replaced. The section in the Bellevue Hill Park, Cincinnati, Ohio, is the type are replaced. Nickles, in characterizing the Bellevue as “Monticulipora molesta beds” Probably erred by misidentifying the abundant Heterotrypa frondosa: M. molesta Nicholson is actually a Peronopora.

Year published: 1979